But with static linked libraries, I cannot switch between
libthread and libthr - right? Could somebody give me an inspiration/
recommendation?

Unless you are ready to count individual CPU cycles, you won't find a
noticable difference between static and dynamic linked executables on
application such as MySQL. You should probably leave them dynamic so you can
experiment with libmap.

If you tried everything from here:
http://wikitest.freebsd.org/moin.cgi/MySQL and still get low results, then
you're out of luck.

BTW, I've updated the page to point at the timestamp wrapper library:
http://www.watson.org/~robert/freebsd/clock/

Still the imperfect prototype, I'd love to see some practical feedback on any
performance impact it has for MySQL or other applications along those lines.
Basically, you preload this library and set an environmental variable to
override the application's selection of clock quality for gettimeofday() and
time().